Simple, yet versatile, methods to functionalize graphene flakes with metal (oxide) nanoparticles are in demand, particularly for the development of advanced catalysts. Herein, based on light-induced electrochemistry, we report a laser-assisted, continuous, solution route for the simultaneous reduction and modification of graphene oxide with catalytic nanoparticles. Electrochemical graphene oxide (EGO) was used as tarting material and electron-hole pair source due to its low degree of oxidation, which imparts structural integrity and an ability to withstand photo-degradation. Simply illuminating a solution stream containing EGO and metal salt (e.g. H2PtCl6 or RuCl3) with a 248 nm wavelength laser produced reduced EGO (rEGO, oxygen content 4.0 at.%) flakes, decorated with Pt (~2.0 nm) or RuO2 (~2.8 nm) nanoparticles. The RuO2-rEGO flakes exhibited superior catalytic activity for the oxygen evolution reaction, requiring a small overpotential of 225 mV to reach a current density of 10 mA cm−2. The Pt-rEGO flakes (10.2 wt.% of Pt) shows enhanced mass activity for the hydrogen evolution reaction, and similar performance for oxygen reduction reaction compared to a commercial 20 wt.% Pt/C catalyst. This simple production method was also used to deposit PtPd alloy and MnOx nanoparticles on rEGO, demonstrating its versatility in synthesizing functional nanoparticle modified graphene materials.